- Krishna Engineering College
95, Loni road Mohanagar, Ghaziabad
Uttar Pradesh-201007 - 09718354423
Jitendra Pal Singh
Manav Rachna, Sciences (Physics), Faculty Member
- G.B.P.U.A.&T., PANTNAGAR, UTTARAKHAND, INDIA, Physics, Department MemberKorea Institute Of Science And Technology, Advanced Analysis Center, Post-DocNational Chung Cheng University, Physics, Post-Docadd
- Jitendra Pal Singhedit
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Abstract Vanadium dioxide (VO2) is one kind of desired thermochromic material for many smart devices because of its notable temperature-responsive infrared modulation and metal−insulator transition with underlying structural phase... more
Abstract Vanadium dioxide (VO2) is one kind of desired thermochromic material for many smart devices because of its notable temperature-responsive infrared modulation and metal−insulator transition with underlying structural phase transition (SPT). Understanding on the tuning of these properties in an anticipated manner is essential to accomplish device realization. Here, we report the annealing time induced modifications in SPT and the thermochromic properties of VO2 thin films. Using RF sputtering deposition, VO2 thin films were grown at room temperature and their ex-situ annealing was carried out at 600 °C for different time from 2 min to 60 min. Structural, electronic and thermochromic properties of these films were investigated. VO2 thin films samples annealed for longer time exhibit larger crystallite size, higher surface roughness and SPT temperature, and the reduced hysteresis width of SPT during heating and cooling cycle. X-ray absorption spectroscopy results indicate that the variation in the annealing time do not alter the electronic structure significantly. Nevertheless, VO2 thin film samples with prolonged annealing display higher IR transmittance modulation across the SPT.
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... Magn. Mater. 256 420 [10] Xue H, Li Z, Wang X and Fu X 2007 Materials Letters 61 347 [11]Roy MK, Halder B and. Verma HC 2006 Nanotechnology 17 232 [12] Singh JP, Srivastava RC, Agrawal HM, Kushwaha RPS, Chand P and Kumar R 2008 Int. ...
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Oxygen-based electrocatalysis is an integral aspect of a clean and sustainable energy conversion/storage system. The development of economic bifunctional electrocatalysts with high activity and durability during reversible reactions... more
Oxygen-based electrocatalysis is an integral aspect of a clean and sustainable energy conversion/storage system. The development of economic bifunctional electrocatalysts with high activity and durability during reversible reactions remains a great challenge. The tailored porous structure and separately presented active sites for oxygen reduction and oxygen evolution reactions (ORR and OER) without mutual interference are most crucial for achieving desired bifunctional catalysts. Here, we report a hybrid composed of sheath-core cobalt oxynitride (CoOx@CoNy) nanorods grown perpendicularly on N-doped carbon nanofiber (NCNF). The brush-like CoOx@CoNy nanorods, composed of metallic Co4N cores and oxidized surfaces, exhibit excellent OER activity (E = 1.69 V at 10 mA cm-2) in an alkaline medium. Although pristine NCNF or CoOx@CoNy alone had poor catalytic activity in the ORR, the hybrid showed dramatically enhanced ORR performance (E = 0.78 V at -3 mA cm-2). The experimental results coupled with a density functional theory (DFT) simulation confirmed that the broad surface area of the CoOx@CoNy nanorods with an oxidized skin layer boosts the catalytic OER, while the facile adsorption of ORR intermediates and a rapid interfacial charge transfer occur at the interface between the CoOx@CoNy nanorods and the electrically conductive NCNF. Furthermore, it was found that the independent catalytic active sites in the CoOx@CoNy/NCNF catalyst are continuously regenerated and sustained without mutual interference during the round-trip ORR/OER, affording stable operation of Zn-air batteries.
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Abstract In present work, atomic diffusion processes in MgO/Fe/MgO structure is investigated. This structure is deposited by using e-beam evaporation method in ultra-high vacuum (10 −7 Torr). X-ray diffraction pattern exhibits amorphous... more
Abstract In present work, atomic diffusion processes in MgO/Fe/MgO structure is investigated. This structure is deposited by using e-beam evaporation method in ultra-high vacuum (10 −7 Torr). X-ray diffraction pattern exhibits amorphous nature of MgO layer, however, Au and Fe layers are polycrystalline in nature. Structural quality investigated using transmission electron microscopy shows the presence of short-ranged crystalline ordering in MgO layer. Oxygen atoms of this layer exhibit its interaction with Mg to form MgO, however, Fe layer exists in metal form with onset of oxidation at interface. Rutherford backscattering study shows the diffusion of atoms from upper layers to the layers underneath and to the substrate. Au atoms exhibit exponential diffusion profile in the structure, however, the compositional variation of Fe atoms is described using the combination of exponential decay and exponential growth functions.
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The role of Ni oxide in the electrocatalytic water oxidation of a nickel(ii) Schiff base (N,N′-bis (salicylidene) ethylenediamino nickel(ii)) is investigated.
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Present work investigates the annealing effects on MgO thin films deposited using e-beam evaporation method. MgO thin films of thickness 5 and 50 nm were evaporated from MgO-pellet in ultra-high vacuum (2×10-8 Torr). As deposited thin... more
Present work investigates the annealing effects on MgO thin films deposited using e-beam evaporation method. MgO thin films of thickness 5 and 50 nm were evaporated from MgO-pellet in ultra-high vacuum (2×10-8 Torr). As deposited thin films exhibit coordination similar to MgO bulk as envisaged from near edge X-ray absorption fine structure measurements. As deposited films were annealed at 300, 400 and 500oC in open environment. Thickness of films remain unaltered with annealing within experimental error. Raman spectroscopic measurements further confirm the presence of bands associated with Mg-O bonding at such low thicknesses.
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Abstract Ceria coated carbon nanotubes (CeO2@CNTs) were prepared as a versatile support material to improve both the activity and stability of platinum (Pt)-based catalysts. We demonstrated that the CeO2 nanoparticles (NPs) had an... more
Abstract Ceria coated carbon nanotubes (CeO2@CNTs) were prepared as a versatile support material to improve both the activity and stability of platinum (Pt)-based catalysts. We demonstrated that the CeO2 nanoparticles (NPs) had an extrinsically remote functionalization effect on the Pt electrocatalysis. The CeO2 modulated the electronic structure, and facilitated the O2 adsorption property of Pt without any intrinsic chemical doping or Pt-alloying. This led to d-band electron filling in Pt, and delivery of active oxygens (O−) to the Pt surface via oxygen spillover at the Pt-CeOx interface, thus enhancing the ORR activity. Furthermore, due to the unique redox behavior between Ce3+ and Ce4+, the dissolved Ce ions could also participate in the radical scavenge reaction, which prevents the chemical degradation of polymeric components in the cell. A single cell using the Pt NPs supported on CeO2@CNT as a cathode catalyst delivered a superior electrochemical performance and a retained durability compared to the cells with pristine CNT supported Pt NPs.
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Abstract Herein, Fe+ and Zn+ ion implantation effects in MgO single crystals were investigated. Slight improvement in the magnetic behavior of implanted single crystals was observed, however, no ferromagnetic hysteresis was observed... more
Abstract Herein, Fe+ and Zn+ ion implantation effects in MgO single crystals were investigated. Slight improvement in the magnetic behavior of implanted single crystals was observed, however, no ferromagnetic hysteresis was observed despite the presence of Fe ions in the lattice. The effect was associated with the oxidation of these ions and possibly due to occurrence of oxygen vacancies. Angle dependent Mg K-edge near edge X-ray absorption fine structure (NEXAFS) measurements reflected the slight change in local electronic structure induced by implantation. Results obtained from O K-edge NEXAFS measurements supported the results obtained from Mg K-edge spectra. These measurements further inferred the interaction between implanted ions and lattice oxygen.
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Abstract Defects play an essential role in controlling the phenomenon of d0 ferromagnetism in nonmagnetic oxides. Defects can have significant impact on behavior, especially d0 ferromagnetism of oxide materials at room temperature (RT).... more
Abstract Defects play an essential role in controlling the phenomenon of d0 ferromagnetism in nonmagnetic oxides. Defects can have significant impact on behavior, especially d0 ferromagnetism of oxide materials at room temperature (RT). Defects in magnesium oxide can be created by various phenomena like ion implantation, swift heavy ion/laser/gamma or UV irradiation, etc. This review focuses on the various characterization tools that are helpful to identify the nature of defects in the materials. Microscopic studies infer about the crystal structure modification via doping concentrations in metal oxides. Tools like ultra-violet visible (UV–Vis) spectroscopy and photoluminescence (PL) spectroscopy enrich the information on defects as well as depict the kind of vacancy. Electron paramagnetic resonance (EPR) is suitable to get information on spin centers in the materials. In addition to this, synchrotron radiation-based techniques like X-ray absorption spectroscopy (XAS), X-ray magnetic circular dichroism (XMCD) are also helpful to know about the structural defects and nature of vacancy in the materials. Vibrating sample magnetometry (VSM)/superconducting quantum interference device (SQUID) measurements deduce the magnetic properties and cause of the ferromagnetism in the metal oxide. Thus, these characterization tools are covered in this review by addressing the origin of defects as well as the methodology utilized to create and control defects in the materials. A detailed understanding of these issues is focused on magnesium oxide, a well-known candidate of the d0 ferromagnetic category.
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Herein, sputtering duration and annealing temperature effects on the structure and local electronic structure of MgO thin films were studied using synchrotron radiation based X-ray diffraction and X-ray absorption spectroscopic... more
Herein, sputtering duration and annealing temperature effects on the structure and local electronic structure of MgO thin films were studied using synchrotron radiation based X-ray diffraction and X-ray absorption spectroscopic investigations. These films were grown at substrate temperature of 350 °C by varying sputtering duration from 25 min to 324 min in radio frequency (RF) sputtering method followed by post-deposition annealing at 400, 600 and 700 °C for 3 h. These films were amorphous upto certain sputtering durations, typically upto 144 min and attains crystallization thereafter. This kind of behavior was observed at all annealing temperature. The textured coefficient of crystalline films envisaged that the orientation was affected by annealing temperature. Coordination of Mg2+ ions was more distorted in amorphous films compared to crystalline films. Moreover, onset of molecular oxygen are absorbed at low annealing temperature on these films.
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Research Interests: Chemical Engineering, Materials Science, Biomedical Engineering, PHOTOELECTRON SPECTROSCOPY, Medicine, and 12 moreDoping, Metal Nanoparticles, Photoluminescence, Zinc Oxide, Silver, Nanostructures, Zinc, Gram Positive Bacteria, XANES, Gram-negative bacteria, Anti-Bacterial Agents, and X Ray Photoelectron Spectroscopy
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Abstract Present work is focused on the study of various physical properties of different phases (α & γ) of Fe2O3 prepared just by varying initial precursors and solvents. Diverse structural and spectroscopic techniques infer growth... more
Abstract Present work is focused on the study of various physical properties of different phases (α & γ) of Fe2O3 prepared just by varying initial precursors and solvents. Diverse structural and spectroscopic techniques infer growth of α-phase using gelatin (GEL) + deionized water (DI) while mixed (α & γ)phase is obtained with GEL + ethylene glycol (EG) as precursor and solvents in iron nitrate salt. By controlling the properties of the solvent media, we have been able to tune the crystallite size from 26.31 nm (α-phase) to 38.87 nm (mixed-phase). The corresponding activation energy for α-phase and mixed-phase was calculated using the Arrhenius plot. Dielectric loss and permittivity in both samples exhibited different behaviour with temperature and which can be explained based on their electronic structure studied by the X-ray absorption spectroscopy technique. The interplay of different phases of materials can be achieved just by controlling the synthesis parameters like solvents/precursors or both.
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Question related to modern physics for B. Tech. Ist year students are given in this file.
This file contains questions alongwith answer related to laser, fiber optics and holography.
File contains model questions alongwith their answers that are important for B. Tech. Ist year student.
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Journal: Vacuum https://www.elsevier.com/journals/vacuum/0042-207x/guide-for-authors#13300 Aims and scope of the Special Issue: Materials with d o electrons are important and represent a wide class of materials. These materials are... more
Journal: Vacuum https://www.elsevier.com/journals/vacuum/0042-207x/guide-for-authors#13300 Aims and scope of the Special Issue: Materials with d o electrons are important and represent a wide class of materials. These materials are utilized for several applications based on their optical and dielectric behavior. Under reduced dimension these materials not only show superiority of these properties but sometimes exhibit magnetism which is neither expected in these materials. This kind of magnetism is termed as d o magnetism. This provides an additional degree of freedom for multifunctional devices. Since, existence of defects is intriguing to this behavior in d o ferromagnetic materials. Hence, purpose of this special issue to collect the articles which emphasis particularly identification of defects in these materials either by experimental or theoretical tools. The defects in these systems occur either by pre-synthesis or post synthesis treatments. The approaches which can generate defects in the materials in controlled manner can also pave up a way to control of this effect. Hence, these approaches can give better understanding of this phenomenon in these materials. The techniques which can effectively identify particular defects in the material are also important to get accurate and concrete information. Thus, this special focuses on the creation of defects in controlled manner and characterization of these materials using advanced characterization tools including synchrotron radiation based technique.